This invention relates generally to wireless communication systems and, more particularly, to IP multicast communication systems incorporating location areas.
Today""s wireless communication systems provide a broad range of services to both individual communication units and groups of communication units while they move about. These services include cellular telephony, group dispatch, and packet data, to name just a few. A typical example of such a system 100 is illustrated in FIG. 1. The configuration shown in FIG. 1 is typical in wireless communications systems such as Global System for Mobile Communications (GSM), Advanced Mobile Phone Service (AMPS), Terrestrial Trunked Radio (TETRA), xe2x80x9cIDENxe2x80x9d, and xe2x80x9cSMARTZONExe2x80x9d systems. As shown, a central switch 101 provides connections between cell sites 104-107.
A plurality of communication units 110-115 (e.g., mobile or portable radios, cellular telephones, personal digital assistants (PDAs)) wirelessly communicate with the sites 104-107 and each other, and are often logically divided into various subgroups or talk groups. In such a system, the call processing management and switching functionality are generally contained within the same physical unit, i.e., the central switch 101. The sites 104-107 are connected to the central switch 101 through dedicated or on-demand links and intermediate processors 102-103 in what is often called a xe2x80x9cstarxe2x80x9d configuration. Some very large systems use a hierarchy of such xe2x80x9cstarsxe2x80x9d where intervening concentrators group the links from multiple cell sites and do some lower level processing on them before passing them up to the central switch.
Oftentimes, particularly in cellular systems, the cell sites are grouped within different multi-cell xe2x80x9clocation areas.xe2x80x9d As shown, cell sites 104, 105 are within location area 116 and cell sites 106, 107 are within location area 117. Alternatively or additionally, communication systems may include certain individual sites that are not grouped with other sites. This is typically the case for private trunking systems. For convenience, these individual sites will be referred to as single-cell xe2x80x9clocation areas.xe2x80x9d
Heretofore, wireless communication networks as described above typically used a centralized mobility management function. In such systems, as communication units move from one location area to another (or, in trunking systems, from one cell site to another) they indicate their movement to the network through handover and location update procedures. The location change information is forwarded to a hierarchical network of location databases, usually called visitor location registers (VLRs) and home location registers (HLRs). The centralized connection management functionality in the switching hub uses this location information to determine which cell sites need to be included when a call request is made. In the instance where communication units move among cells within a location area (i.e., without crossing location area boundaries), the communication units do not automatically update their location to the infrastructure. This is done to save control channel capacity at the expense of requiring a paging sequence at the start of calls. The VLR is relied upon to keep track of which location area each communication unit is located in so that cells in the right location areas can be paged when needed for a call.
Next-generation wireless systems propose to employ multicast addressing protocols, such as multicast Internet Protocol (IP) for providing group or dispatch call services. Multicast IP may also be used for traditional cellular systems supporting interconnect/individual calls. Examples of IP Multicast communication systems include the referenced U.S. patent application Ser. No. 09/283,121, now issued as U.S. Pat. No. 6,141,347; and U.S. patent application Ser. No. 09/464,269, titled xe2x80x9cMethods for Implementing a Talkgroup Call in a Multicast IP Network,xe2x80x9d each of which is assigned to Motorola, Inc. and incorporated herein by reference in its entirety.
Generally, IP multicasting protocols are considered to be more efficient and less costly than traditional circuit-switched networks. The multicast IP network defines a distributed, rather than centralized, connection and mobility processing environment where there is no centralized location register (VLR/HLR). Rather, mobility information is inherent to the packet network as communication units register or de-register individual or group affiliations with cells, and the cells join or leave multicast IP addresses to participate in traffic for the communication units. The benefits of a distributed connection and mobility processing environment include fully localized resource management, fully distributed mobility management and easy network scalability.
While distributed connection and mobility processing networks such as multicast IP networks offer several advantages relative to traditional circuit-switched networks, they do not presently support the concept of multi-cell location areas. That is, communication units in a multicast IP network are presently required to register affiliations each time they enter a new cell. It would be desirable to provide multi-cell location areas in multicast IP networks, analogous to those described in circuit-switched systems, whereupon communication units initially registered in a cell of a location area may roam to other cells within the location area without registering affiliations with each new cell.
Therefore, a need exists for a system and methods of distributed connection and mobility processing for multi-cell location areas. Preferably, the system and methods would enable a communication unit to register affiliations and/or location updates only upon entering a new location area to save control channel capacity. Advantageously, a paging sequence would be initiated at the start of calls without relying on a centralized entity such as a VLR to keep track of which communication units should be paged. The present invention is directed to satisfying these needs.